1. Field of the Invention
This invention relates to a waterproof structure of a lens barrel of a camera wherein a movable lens barrel member is designed to move forwardly and backwardly over a comparatively large distance such as a lens barrel of a two-focal length change-over lens, a zoom lens or a collapsible mount type lens.
2. Description of the Prior Art
A waterproof camera conventionally employs, as a waterproof or dustproof structure of a movable lens barrel, an O-ring or a fold type bellows.
An exemplary one of conventional waterproof structures which employ an O-ring is shown in FIGS. 10 and 11. Referring to FIGS. 10 and 11, a fixed lens barrel member 1 is secured to a body of a camera not shown, and a movable lens barrel member 4 having a main lens 5 carried therein is disposed in the fixed lens barrel member 1 for sliding movement in the direction of an optical axis of the main lens 5.
A pair of O-rings 2 and 3 are mounted on front and rear faces of an annular rib 1a formed on an inner face at a front end portion of the fixed lens barrel member 1. In a condition shown in FIG. 10 wherein the movable lens barrel member 4 is accommodated in the fixed lens barrel member 1, that is, in a wide angle photographing or collapsed condition, the O-ring 2 on the front face of the annular rib 1a of the fixed lens barrel member 1 contacts with an annular rib or flange 4a formed at the front end of the movable lens barrel member 4 to establish a liquid-tight condition. To the contrary, in another condition shown in FIG. 11 wherein the movable lens barrel member 4 is advanced or projected forwardly from the fixed lens barrel member 1, that is, in a tele-photographing or non-collapsed condition, the other O-ring 3 on the rear face of the annular rib 1a of the fixed lens barrel member 1 contacts with another annular rib or flange 4b formed at the rear end of the movable lens barrel member 1 to establish a liquid-tight condition.
An exemplary one of conventional waterproof structures which employ a fold type bellows is shown in FIGS. 12 and 13. Referring to FIGS. 12 and 13, a fold type bellows 12 made of a material which can maintain a liquid-tight condition such as rubber or rubber-coated cloth is connected at a rear end thereof to an annular rib 11a formed at a rear end portion of a fixed lens barrel member 11 and at the other front end thereof to an annular rib or flange 14a formed at the front end of a movable lens barrel member 14. When the movable lens barrel member 14 is retracted to a wide angle photographing or collapsed position as shown in FIG. 12, the fold type bellows 12 is accommodated in a folded condition in a spacing formed by and between the annular rib 11a at the rear portion of the fixed lens barrel member 11 and the annular flange 14a at the front end of the movable lens barrel member 14 as seen in FIG. 12. To the contrary, when the movable lens barrel member 14 is projected to a tele-photographing or non-collapsed position as shown in FIG. 13, the fold type bellows 12 is extended following the movement of the movable lens barrel member 14. The fold type bellows 12 thus maintains the liquid-tight condition between the fixed lens barrel member 11 and the movable lens barrel member 14 in this manner.
The former conventional waterproof structure which employs an O-ring has a drawback that, when the movable lens barrel member is at an intermediate position between the fully retracted position and the fully advanced position, the liquid-tight condition thereof cannot be maintained because the O-rings do not contact sufficiently with the movable lens barrel member.
It may seem recommendable, in order to maintain the liquid-tight condition at any intermediate position of the movable lens barrel member of the waterproof structure, to continuously apply a pressure so as to normally contact an outer periphery of the movable lens barrel member 4 with an inner periphery of the fixed lens barrel member 1. In this instance, however, such pressure makes a high load to the movable lens barrel member 4 when the movable lens barrel member 4 moves forwardly or backwardly. Accordingly, there is a drawback that a motor of large size and a power source of a large capacity are required, which will lead to an increase in overall size of the camera.
To the contrary, the latter conventional waterproof structure which employs a fold type bellows requires, between the movable lens barrel member 14 and the fixed lens barrel member 11, a spacing for accommodating the folded bellows 12 therein. Accordingly, there is a drawback that the fixed lens barrel member 11 is required to have an increased size, which also leads to an increase in overall size of the camera.